A complementary half-bridge type inverter circuit with an N-type field effect transistor and a P-type field effect transistor that are connected in series is widely known to those skilled in the art. The sources of the N-type field effect transistor and the P-type field effect transistor of the inverter circuit are interconnected, while the gates of these transistors, too, are interconnected. The drains of the N-type and P-type field effect transistors are respectively connected to the positive electrode and the negative electrode of a DC power source.
An example of inverter circuits of this type described in Japanese Patent Laid-open No. 2003-18850, wherein an N-type field effect transistor and a P-type field effect transistor are contained in a single package with their terminals exposed to the outside. In this state, the N-type field effect transistor and the P-type field effect transistor serve as a switching element. The switching element is mounted on a circuit board in an upright position on the circuit board. The gates of the N-type and P-type field effect transistors are connected to a gate control circuit that is comprised of various components mounted on the circuit board.
As there is a demand for further miniaturization of a self-ballasted fluorescent lamp, it is necessary to reduce the dimensions of its inverter circuit even further. In order to achieve this, the switching element has to be made even more compact.
However, a switching element formed by merely placing both an N-type field effect transistor and a P-type field effect transistor in one package and mounting the package in an upright position on a circuit board as described in Japanese Patent Laid-open No. 2003-18850 presents problems in that there are limitations in how small the switching element can be made, because the lead terminals of the element require a certain degree of thickness in order to ensure sufficient mounting strength of the element. Furthermore, although Japanese Patent Laid-open No. 2003-18850 mentions using a switching element of a surface mounting type, there is no description of concrete measures to make the switching element compact nor discussion about performance of the switching element should it be used in an inverter circuit for a self-ballasted fluorescent lamp.
In order to solve the above problems, an object of the present invention is to provide a self-ballasted fluorescent lamp with improved mounting efficiency, and a luminaire including such a self-ballasted fluorescent lamp.